A conventional lighting unit for use in, for example, a vehicle headlight is disclosed in Japanese Patent No. 4047266 (or U.S. Pat. No. 7,165,871B), in which a semiconductor light emitting device and a fluorescent material are used in combination. The lighting unit disclosed in this patent document can be configured such that the fluorescent material is excited by the light from the semiconductor light emitting device to emit visible light and the visible light is reflected by a reflector forward to form a predetermined light distribution pattern.
However, the above conventional lighting unit form a single light distribution pattern because the light emission performance of the fluorescent material and the reflection performance of the reflector and the like are constant.
To cope with this, a plurality of fluorescent materials formed like a color wheel are utilized to be switched for forming a plurality of different light distribution pattern. With this configuration, unintended light may leak from areas between the plurality of fluorescent materials. The leakage light is typically shut down by shielding the areas between the plurality of fluorescent materials. This requires an additional shielding member or the like. However, when such a shielding member is disposed so as to be capable of shielding leakage light, the shielding member may be heated by the light from the semiconductor light emitting device with high luminous flux density, resulting in heat deformation. In view of this, the light from the semiconductor light emitting device is desired to always be concentrated onto the fluorescent material without shielding. However, in this case, the separate fluorescent materials may not be effectively irradiated with the light, meaning that the light from the semiconductor light emitting device cannot be utilized with a high utilization rate. Accordingly, both the case with the light shielding member and the case without the light shielding member can have certain problems.